1. Field of the Invention
The present invention relates to a liquid crystal display device which may be incorporated in audio visual (AV) apparatuses, office automation (OA) apparatuses, or the like. The present invention also relates to a method for producing the liquid crystal display device.
2. Description of the Related Art
An active matrix liquid crystal display device includes a TFT substrate which includes picture element electrodes, and thin film transistors (hereinafter, simply referred to as xe2x80x9cTFTsxe2x80x9d) connected to the picture element electrodes formed on a glass substrate in a matrix. The active matrix liquid crystal display device further includes a counter substrate on which counter electrodes are formed. The TFT substrate and the counter substrate are adhered to each other with a sealing material, with a liquid crystal material interposed therebetween.
FIG. 6 is a simplified plan view of the TFT substrate of a conventional liquid crystal display device. FIG. 7 is a plan view of the counter substrate of the conventional liquid crystal display device.
Referring to FIG. 6, the TFT substrate includes a glass substrate 1 and picture element electrodes 6 arranged on the glass substrate 1 in a matrix so as to correspond to an image display region 8.
Herein, xe2x80x9can image display regionxe2x80x9d refers to an area of a substrate corresponding to a display region of a liquid crystal display device from where a viewer can actually see a displayed image.
Each of the picture element electrodes 6 is connected to corresponding one of a plurality of gate bus lines 2 and corresponding one of a plurality of source bus lines 4. The TFT substrate further includes a gate driver GD for supplying scanning signals to the gate bus lines 2 and a source driver SD for supplying data signals to the source bus lines 4.
Referring to FIG. 7, the counter substrate includes a glass substrate 20, and color filters 12 provided on the image display region 8 of the glass substrate 20 so as to correspond to the picture element electrodes 6 on the TFT substrate. Counter electrodes (not shown) made of a transparent conductive film are formed on the color filters 12. The liquid crystal material interposed between the TFT substrate and the counter substrate is switched in accordance with a potential difference between the picture element electrodes and the corresponding counter electrodes. Light shielding layers (not shown) which act as so-called black matrix, are formed on the counter substrate for shielding light incident to the TFTs and light leaking from gaps between each picture element electrode.
Generally, a light shielding frame section 14 is provided on the counter substrate around a periphery of the image display region 8 for shielding unnecessary light incident to the periphery of the image display region 8. Since the liquid crystal display device uses back light, in the case where the light shielding frame section 14 is not provided, the unnecessary light reaches to the TFTS, thereby deteriorating the OFF characteristics of the TFTs, and thus deteriorating the display quality of the liquid crystal display device as well.
The TFT substrate and the counter substrate are adhered to each other with a sealing resin 16 which is provided in the vicinity of the light shielding frame section 14. A UV curable sealing resin is often used as the sealing resin 16. In this case, UV light is radiated from the counter substrate side toward the TFT substrate side, or the TFTs are damaged and the characteristics thereof are deteriorated by the UV light in the step of adhering the substrates. Furthermore, in the case of using the UV curable sealing resin, the size of the light shielding frame section 14 is limited in order that the sealing resin 16 can be irradiated with UV light. However, smaller size of the light shielding frame section 14 necessitates higher alignment accuracy in assembling the light shielding frame section 14 with the module, which renders this step of adhering the substrates complicated.
In order to overcome the above-described problem, a technique is proposed, for example, in Japanese Laid-Open Publication No. 6-175157, in which a light shielding frame section is formed on a TFT substrate.
However, according to the above-described technique, although the light shielding frame section is formed on the TFT substrate, color filters for displaying colors or light shielding layers (black matrix) need to be formed on a counter substrate. In this case, a sealing margin of the TFT substrate and the counter substrate is as small as about 3 xcexcm, which necessitates use of a large scale sealing apparatus.
According to one aspect of the present invention, a liquid crystal display device is provided which includes: a first substrate; a second substrate; and a liquid crystal layer interposed between the first substrate and the second substrate. The first substrate includes a plurality of switching elements, a plurality of picture element electrodes connected to the plurality of the switching elements and a plurality of color filters which are arranged so as to correspond to the plurality of the picture element electrodes on an area of the first substrate corresponding to a display region of the liquid crystal display device, and a light shielding frame layer around a periphery of the display region. Accordingly, there is no need for forming color filters and a light shielding frame layer on a second substrate.
In one embodiment of the present invention, the first substrate further including light shielding layers on the switching elements, for shielding light incident to the switching elements. Accordingly, there is no need for providing a light shielding layer on the second substrate.
In one embodiment of the present invention, the light shielding layers and the light shielding frame layer are made of a same material. Accordingly, the light shielding layers and the light shielding frame layer are formed in one step.
In one embodiment of the present invention, the light shielding layers and the light shielding frame layer are formed through an electrochemical reaction. Accordingly, the light shielding layers and the light shielding frame layer are easily formed.
In one embodiment of the present invention, the light shielding frame layer includes a plurality of colored layers of different colors. According to one embodiment of the present invention, the plurality of colored layers of different colors are made from material used to form the plurality of color filters. Accordingly, the light shielding frame layer is formed of colored layers made of the same materials as the color filters, and thus the light shielding frame layer and the color filters are simultaneously formed.
In one embodiment of the present invention, the first substrate further includes a driving circuit for driving the switching elements, and the light shielding frame layer is formed over the driving circuit. Accordingly, light incident to the driving circuits is shielded by the light shielding frame layer.
According to another aspect of the present invention, a liquid crystal display device is provided which includes: a first substrate; a second substrate; and a liquid crystal layer interposed between the first substrate and the second substrate. The first substrate includes a plurality of switching elements, a plurality of picture element electrodes connected to the plurality of the switching elements and light shielding layers on the switching elements on an area of the first substrate corresponding to a display region of the liquid crystal device, and a light shielding frame layer around a periphery of the display region.
In one embodiment of the present invention, the light shielding layers and the light shielding frame layer are made of a same material.
According to still another aspect of the present invention, a method for producing a liquid crystal display device is provided, the liquid crystal display device including a first substrate, a second substrate, and a liquid crystal layer interposed between the first substrate and the second substrate. The method includes the steps of forming a plurality of switching elements, a plurality of picture element electrodes connected to the plurality of the switching elements and a plurality of color filters which are arranged so as to correspond to the plurality of the picture element electrodes on an area of the first substrate corresponding to a display region of the liquid crystal display device, and a light shielding frame layer on the first substrate around a periphery of the display region. Accordingly, there is no need for forming color filters and a light shielding frame layer on a second substrate.
In one embodiment of the present invention, the step of forming the color filters and the step of forming the light shielding frame layer are conducted as the same step. Accordingly, the color filters and the light shielding frame layer are formed in one step.
In one embodiment of the present invention, the method further includes a step of forming light shielding layers on the first substrate. Accordingly, there is no need for providing a light shielding layer on the second substrate.
In one embodiment of the present invention, the step of forming the light shielding layers and the step of forming the light shielding frame layer are conducted as the same step. Accordingly, the light shielding layers and the light shielding frame layer are formed in one step.
In one embodiment of the present invention, the step of forming the light shielding layer and the step of forming the light shielding frame layer employ an electrochemical reaction. Accordingly, the light shielding layers and the light shielding frame layer are easily formed.
In one embodiment of the present invention, the step of forming the light shielding frame layer includes a step of superimposing, at least partially, a plurality of colored layers of different colors.
According to still another aspect of the present invention, a method for producing a liquid crystal display device is provided, the liquid crystal display device including a first substrate, a second substrate and a liquid crystal layer interposed between the first substrate and the second substrate. The method includes the steps of forming a plurality of switching elements, a plurality of picture element electrodes connected to the plurality of the switching elements and light shielding layers on the switching elements on an area of the first substrate corresponding to a display region of the liquid crystal display device, and a light shielding frame layer on the first substrate around a periphery of the display region.
In one embodiment of the present invention, the step of forming light shielding layers and the step of forming the light shielding frame layer are conducted as the same step.
Thus, the invention described herein makes possible the advantages of providing: (1) a liquid crystal display device which includes a counter substrate that can be easily formed, and in which the counter substrate and a TFT substrate are easily adhered to each other; and (2) a method for producing the liquid crystal display device.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.